1. Field of the Invention
The present invention relates generally to drive systems and, more particularly, to a drive system particularly useful in machines incorporating air bearings and characterized by zero backlash, by introducing no vibrations or noise into the moving structures, and one that requires no lubrication.
2. The Prior Art
Precision machines require precision drives. Precision machines include precision cutting and forming tools, positioning and coordinate measuring machines and surface analysis systems. In precision machines, it is required that one movable part traverses an extremely accurately defined path relative to another part. The movable part's traverse is facilitated by air bearings. Air bearings provide a virtually friction-free guide, see U.S. Patent Nos. 3,578,827 and 4,378,134. Drive systems for such precision machines employing air bearings must be inherently "quiet," however. By the term "quiet," it is meant to define a drive system which introduces no vibrations into the parts and structures it is designed to move. This requirement for quiet drive systems derives from the fact that air bearings inherently possess little or no damping. Due to the lack of sufficient damping, air bearings are most sensitive to vibrations at certain frequencies. Such vibrations and noise adversely affect the performance of these precision machines. Gear drives do introduce such vibrations and noise. Precision machines also require the ability to position the movable parts along the accurately defined path relative to another part. This is accomplished using positioning servos, which require minimal backlash in the drive. Gear drives suffer from backlash, which make them unsuitable for precision machines. The requirement for quiet, non-backlash drive systems in air bearing machines is and remains a compelling consideration for designers of such machines.